THE SYNCHRONOUS DISCOVERY OF DEEP TIME AND DEEP SPACE, AND THE RESULTING SHIFT IN FUNDAMENTAL RESEARCH QUESTIONS IN GEOLOGY AND ASTRONOMY

Prior to the late eighteenth century, there was no significant historical aspect to the study of the natural world. It was during the nineteenth century that the universe and Earth acquired their scientific historicity. In the case of geology, in the seventeenth century Steno established the basic principles of reconstructing Earth history, but his work was premature, in the sense that natural philosophers of his day were not yet ready to embrace Steno’s principles and put them to work interpreting the history of the Earth. In astronomy, Galileo’s telescope and his writings stimulated debate in the seventeenth century about the mechanics of the solar system, but historical questions were not components of this debate.

In the early 1830s Charles Lyell published his three-volume Principles of Geology, which helped to establish the concept of deep geologic time. At about the same time, in 1838, German astronomer Friedrich Bessel became the first person to measure the distance to a star outside our solar system. Using stellar parallax, Bessel measured the distance to the star 61 Cygni to be 66 trillion miles. Twenty-one years later, in 1859 (the year of publication of Darwin’s Origin), spectroscopic analysis of light from stars was developed, permitting astronomers to study the characteristics of stars, and also to measure their distances. By the beginning of the twentieth century, the discovery of radioactivity had quashed Lord Kelvin’s constraints about the age of the Earth, and geologists were free to think in terms of previously unimaginable time scales. A comparably liberating event came to astronomy in 1925, with Edwin Hubble’s discovery of stars beyond the Milky Way galaxy.

Because of the discovery of deep space and deep time, geologists and astronomers of the twentieth and twenty-first centuries have addressed fundamentally different types of questions than had been addressed earlier. In the terminology of G. G. Simpson, there was a shift from research questions that exclusively dealt with immanent properties of Earth and the cosmos, to questions that addressed configurational change through time.